Magnetic blowout for circuit breakers



y 1962 D. 1. BOHN 3,033,963

MAGNETIC BLOWOUT FOR CIRCUIT BREAKERS Filed March 18, 1960 5 Sheets-Sheet 1 INVENTOR. DON/1L0 I. Bah N e/vz fkezaGeza d JaFFE/V ATTORNEY y 8, 2 s D. I. BOHN 3,033,963

MAGNETIC BLOWOUT FOR CIRCUIT BREAKERS Filed Match 18, 1960 5 Sheets-Sheet 2 INVENTOR. 00/10/40 I. aa/m/ B 1 0s news/v4.3 5455x6505 g-GFFE/I d TTOR NE Y May 8, 1962 Filed March 18, 1960 D. l. BOHN MAGNETIC BLOWOUT FOR CIRCUIT BREAKERS 5 Sheets-Sheet 3 INVENTOR. flJ/Vfl LA I 506% ea; av: flan 49 4 JEFF 57 41 501: NE

SSheetS-Sheet 4 film/4L0 I. 506

ATTOR May 8, 1962 D. BOHN MAGNETIC BLOWOUT FOR CIRCUIT-BREAKERS Filed March 18, 1960 R. m U m |H\M 7 a 4. 1 v m 9 n uz m M m m E I u 1 m 7 I a1 a Ma s, 1962 Filed March 18, 1960 D. l. BOHN MAGNETIC BLOWOUT FOR CIRCUIT BREAKERS 5 Sheets-Sheet 5 Unite Stats My invention relates to a novel magnetic blowout means for circuit breakers and more specifically relates to a magnetic blowout structure for D.-C. circuit breakers which is formed of a substantially fiat plate having a relatively small window therein and generates a unidirectional magnetic field within the area through which the are formed by separating circuit breaker contacts is moved wherein the magnetic field is initially highly concentrated at the contact area when the circuit breaker contacts begin to separate. The application specifically is a continuationin-part application of my co-pending application Serial No. 698,500 filed November 25, 1957 Circuit breakers of the type which may be equipped with my novel blowout plate are typical high speed current limiting circuit breakers which can, for example, be rated between 3,000 to 6,000 amperes at up to 1,000 volts D.-C.

Magnetic blowout structures for circuit breakers are well known in the art, and typical examples thereof are shown in US. Patents 2,381,637, 2,412,247 and 2,486,104, all of which are assigned to the assignee of the instant invention. In general, these patents show a magnetic blowout structure which comprises a pair of primary blowout coils in parallel and a pair of secondary blowout coils also in parallel.

The primary blowout coils have a relatively small diameter and are positioned adjacent to the circuit breaker cooperating contact area. The purpose of these primary blowout coils is to create a high initial magnetic flux adjacent to the cooperating contacts at the instant an arc is struck between the separating cooperating contacts, and thus create a strong initial force to drive the arc into an arc chute means. However, once the arc travels above the diameter of this first blowout coil, it will encounter reverse flux tending to drive the arc back toward the contact area. This, of course, would prevent extinction of the arc and could cause destruction of the circuit breaker and severe damage to the load protected thereby, as Well as the source feeding into the load.

For this reason, a jump gap means is provided for causing current transfer from the first blowout coil to the second blowout coil which has a substantially larger diameter than the first. This jump gap means operates when the initial are approaches the outer diameter of the first blowout coil, and the magnetic field for driving the arc up into the arc chute is thereafter generated by the second blowout means which has the relatively larger diameter. Thus, the arc will move within a magnetic field having the same direction as did the magnetic field of the first blowout coil.

This above type of structure has two disadvantages; first, a relatively complex and expensive structure of a first and second blowout coil is required; and, second, a jump gap means or transfer means for transferring current from the first blowout means to the second blowout means is required. As well as being a relatively costly structure, it is readily seen that the system including the jump gap is susceptible to failure and requires continuous observation and maintenance.

The primary object of my invention is to provide a novel magnetic blowout structure which, as in the case of the above-described structure, will provide a concentrated magnetic flux in the contact area upon initiation of contact operation and will further cause a unidirectional magnetic field to be generated throughout the blowout area for causing the arc to be continuously elongated in the arc chute.

In the preferred embodiment of my invention, I construct the blowout means of a pair of substantially U- shaped fiat plates which are connected in parallel with each other and in series with the cooperating contacts and positioned adjacent thereto. I have found that in using such a structure where a relatively small stamped opening is placed within a relatively large fiat conductive sheet, the plate will generate an extremely high magnetic flux within the contacting area at the moment of contact separation and during a relatively high rate of rise of current through the plate; and further that the flux created by the plate will be unidirectional through all areas of arc motion when the arc is driven into its cooperating arc chute.

It is to be noted that the invention is not to be construed to the mere use of a stamping for the blowout coil. This concept in itself is old and is shown, for example, in US. Patent No. 2,200,070 to Armstrong et al.

The stamped blowout plate of the present invention more specifically is provided with a relatively small window in a relatively large area plate. In addition, the particular configuration of the stamped plate of the invention is such that the dimension from the opening or window in the plate and in the direction in which the arc is to be moved is of substantially the same order of magnitude as is the diameter across the opening in this same direction.

I do not mean to be limited here to a case where these two dimensions are equal to one another as is the case in the preferred embodiment of the invention, it being noted that some deviation is permissible. It is, however, necessary that the dimension of the plate in the direction of motion of the are be a substantial dimension whereby the plate operates initially as a small diameter coil and thereafter operates as a large diameter coil without the necessity for two individual coils and an arc transfer means for transferring current from the small diameter coil to the large diameter coil.

As pointed out above, presently existing stamped coil devices have been formed with their sole purpose being to replace the normally used wire conductor, such as a wire having a circular cross-section, whereby the stamped construction is highly economical and forms a rigid and self-supporting coil. In these prior devices, however, the concept has been to cut out substantially all of the internal area of the plate and to leave merely the outer rim of the plate to serve as the conductor. That is to say, the stamped coil is formed so that there is a relatively large area window in the surface of the plate as contrasted to my small area window in the plate which leads to highly unusual and unobvious results.

More specifically, since there is a small opening in the plate relative to the plate area in the present device, an exceedingly intense magnetic field will be generated in the contact area at the instant of contact separation which is initiated by a fault current. A preferred theory to explain this operation is that this intense magnetic field is generated since at the initiation of the fault and with a high positive rate of rise of current, the current density in the cross-section immediately adjacent to the window of the plate is high, while the current density in the outer periphery of the plate is relatively low at this time. This is the equivalent of having a small diameter blowout coil which previously was provided for this purpose.

As the arc is drawn by the separating contacts and moved upwardly under the influence of the magnetic field generated by the blowout plate, the rate of rise of current in the arc decreases and begins to go negative as the arc raises in the arc chute. With this change in the rate of rise of current, the point of maximum current density in the circular current path defined by the blowout plate also moves upwardly along the arc. Thus, the magnetic field for controlling and elongating the arc remains unidirectional with respect to the arc and follows the arc upwardly to ensure continued stretching and to prevent a reverse motion of the arc downwardly as could be the case in other types of circuit breakers.

This is the equivalent of substituting a large diameter blowout coil for the previously operative small diameter blowout coil and is done automatically and without jump gap or are transfer means.

It is to be noted that this type of phenomenon will happen to an extremely small extent in the stamped blowout plates of the prior art wherein only a relatively narrow rim is left because of the stamping of a relatively large window. Indeed, the same phenomenon would ocour in any typical'circuilar cross-section conductor. The effect, however, of the outwardly travelling high density filament of current is so small as to be of relatively no use in the assistance of interruption of the are.

In the stamped plate proposed by the present invention, however, the structure takes full advantage of this phenomenon by using a small area window and by providing a relatively large dimension for the plate from the opening in the plate and in the direction of motion of the arc.

Therefore, my novel structure has the advantage of the heretofore described double coil system which is the provision of a relatively high magnetic field at the moment of contact separation, while still providing a unidirectional flux through the complete area of arc motion without the requirement of a jump gap or current transfer means.

A mathematical analysis of the above-noted operation of my novel magnetic blowout means follows when considering the flat blowout plate having an aperture therein as forming an infinite number of parallel connected circuits. Each of these circuits has an inductance and resistance determined in accordance with the length of the particular path under consideration. Those circuits adjacent the contacting area will have a smaller resistance and inductance than those further away from the contacting area, in view of their smaller length.

Since each of the assumed circuits is connected in parallel, the voltage drops across them will be equal to one another and equal to the sum of the resistive voltage drop plus the inductive vector voltage drop. Thus, the voltage drop across any assumed filamentary circuit will be equal to:

where v is the voltage drop, L and r are the inductance and resistance, respectively, of

the filament,

From the above relation, it is seen that the current through the filament circuits is proportional to the difference in the voltage drop v across the filament, and the inductance of that filament multiplied by the rate of change of current therethrough.

When a fault condition appears on the protected line,

there will be a very high positive rate of change of current. The difference between the voltage across the filament and the inductance multiplied by the rate of change of current in the filament will be greater for those inner filaments having a smaller inductance. Hence, at this initial time,

the current flow through the inner filaments will be higher than that through the outer filaments and a relatively strong local magnetic field will be generated at the contact area adjacent these inner filaments.

When the arc current reaches its peak value, however, and the rate of change of current reverses and becomes negative, the current in any filament is proportional to the sum of the filament voltage v and the inductance of the filament times the rate of change of current therethrough. Therefore, the current in the outer filaments having a relatively high inductance will be greater than that of the inner filaments so that the magnetic field at the area adjacent the outer portions of the plate will be increased. This increase of field strength occurs just at the time it is needed, since at this time, the arc has been stretched into the outer regions adjacent the outer filamentary circuits of the plate. Hence, in essence, my novel blowout plate operates to generate a strong magnetic field at the area in the blowout structure at which the arc is being conducted, the increase in the magnetic field following the movement of the arc.

It is to be noted that the above explanation of the operation of my novel blowout structure presently appears to be correct. However, other influences not described herein and not presently understood may be operative in achieving the novel and unexpected operation which has been observed.

According, an important object of my invention is to provide a novel magnetic blowout means which creates a unidirectional flux throughout a blowout area with an initial high concentration of magnetic flux at the contact area.

Another object of my invention is to provide a novel magnetic blowout means for generating a unidirectional flux in a blowout area without the use of arc transferring means.

A further object of my invention is to provide a simplified blowout means which is formed of a simple plate which defines a circular current path.

Another object of my invention is to provide a novel magnetic blowout means which is formed of a substantially U-shaped plate of conductive material.

A further object of my invention is to provide a novel magnetic blowout means which provides a unidirectional flux throughout a blowout area wherein the concentration of flux density is shifted from a central portion adjacent contacting area toward outer portions during the progress of the lengthening of the are.

A further object of this invention is to provide a novel flat plate blowout means which is formed of a plate having a relatively. small aperture therein to define a relatively circular current path.

A further object of my invention is to provide a novel fiat plate blowout coil which is formed of a plate having a relatively small Window stamped therein wherein the dimension from the opening of the window and in the direction of the motion of an arc of the plate is of substantially the same order of magnitude as is the dimension across the opening in the same direction.

A still further object of this invention is to provide an additional flat plate coil having a relatively small window opening which initially conducts current in the manner of a small diameter coil and thereafter conducts current in the manner of a large diameter coil without current transfer means.

Yet a further object of this invention is to provide a novel flat plate blowout coil having a small opening stamped therein which is characterized in initially operating upon theinitiation of a fault current and separation of cooperating contacts as a small diameter blowout coil and thereafter acts as a large diameter blowout coil without the requirement of current transfer means.

As was seen from the above, the essence of my inven tion is to provide a blowout means formed of a simple stamped plate of conductive material. It will, however,

be apparent to those skilled in the art that other U-shaped plates may be associated with the single plate in a manner analogous to the use of a plurality of turns in a blowout coil whereby the unidirectional flux density created by the blowout will be increased.

It may be further desirable to position material having a relatively high magnetic permeability adjacent the contacting area whereby the flux density at this area during initiation of contact operation may be increased. If desired, this magnetic material could be incorporated into the U-shaped conductive plate so as to form a unitary member.

Accordingly, a still further object of my invention is to provide a magnetic blowout formed of a plurality of U-shaped plates connected in series with one another and defining a spiral path of more than one turn for current flow through said plates.

A still further object of this invention is to adapt my novel U-shaped blowout plate with an insert of magnetic material adjacent the contact area which operates to concentrate magnetic fiux during the initial operation of the circuit breaker contacts.

These and other objects of my invention will become apparent from the following description when taken in connection with the drawings in which:

FIGURE 1 shows a plan view of a D.-C. circuit breaker employing my novel blowout means.

FIGURE 2 is an exploded perspective view of my novel I blowout structure in the circuit breaker of FIGURE 1.

FIGURE 3 is a side view of the arc chute structure of the circuit breaker of FIGURE 1 which is associated with my novel magnetic blowout means.

FIGURE 4 is a side view of my novel magnetic blow out plate means.

FIGURE 5 is a top view of the magnetic blowout means of FIGURE 4 as used in the structure of FIGURE 1.

FIGURE 6 is a partially schematic view of the manner in which my novel blowout means is connected in circuit relation with respect to the circuit breaker cooperating contacts.

FIGURE 7 is a side view of FIGURE 6 and particularly illustrates the distribution of the magnetic field created by my novel magnetic blowout means.

FIGURE 8 shows a second embodiment of my novel invention wherein a second plate is added to the plate of my novel invention to form the equivalent of a two-turn coil.

FIGURE 9 is a side view of FIGURE 8.

FIGURE 10 shows a further embodiment of my novel invention in which a piece of magnetic material is inserted in the conductive plate at the portion adjacent the cooperating contacts.

FIGURE ll is a side cross-sectional view of FIGURE it) taken across the lines 11-11.

FIGURE 1 sets forth my novel blowout structure in conjunction with a D.-C. circuit breaker of the type set forth in US. Patent No. 2,891,123 issued June 16, l959, entitled High Speed Circuit Breaker, to C. I. Clausing, assigned to the assignee of the instant invention. Since details of the circuit breaker construction have been fully set forth in the above-noted patent, the reference to the circuit breaker structure will be of a general nature, and reference is made to the above-noted patent for further details with regard thereto.

In general, the circuit breaker structure of FIGURE 1 includes a base member 20 which contains an operating mechanism seen generally at numeral 22 and supports the contact mechanism and circuit breaker terminals from a support post 24. The operating mechanism more specifically comprises a toggle linkage including links 26 and 28 which are operable from a plunger operated by solenoid mechanism 36, with the output of the toggle linkage associated with a magnetic latch structure 32 which is constructed to transmit the motion of the toggle linkage to a pivotally mounted beam member 34 which is attached to the movable contact 36. Movable contact 36 is pivotally movable about pivotal support 33 responsive to rotation of beam member 34.

As will be seen by reference to the above noted patent, the magnetic latch structure includes a coil operating means 46 and is operable in such a manner as to maintain the movable contact 36 in engaged position with respect to stationary contact 42 against the force of a contact opening biasing spring 44. When the electrical energizing structure of the magnetic latch means 32 is energized in a predetermined manner, the latch structure will be defeated, and spring 44 will drive movable contact 36 to a disengaged position with respect to stationary contact 42.

My novel blowout structure is seen in FIGURES 1 through 5 as comprising conductive plates 46 and 48, respectively (see FIGURE 5 for plate '48), which are positioned on either side of cooperating contacts 36 and 42.

It will be noted that for purposes of structural strength, the peripheral edges of the plates 46 and 48 are bent outwardly to form flanges, such as flanges 50 and 52 of plate 46, and flanges 54 and 56 of plate 48 (see FIGURES 2 and 5). While the plates could be stamped from a unitary sheet of conductive material, the plates 46 and 48 set forth herein have been formed of a first and second conductive sheet, such as conductive sheets 58 and 60 for blowout plate means 46, as may be best seen in FIGURES 2, 4 and 5. These sheets are mechanically and electrically fastened together in any desired manner and operate in the exact manner that a single plate would operate.

The circuit breaker current path which includes my novel magnetic blowout structure is schematically illustrated in FIGURE 6 as coming from a first terminal point 62, the substantially U-shaped blowout plates such as blowout plates 46 and 48 (FIGURE 2), the stationary contact schematically indicated as stationary contact 64, the movable contact schematically indicated as movable contact 66 and pivotally mounted at pivot point 68, and thence to a second terminal 74 Thus, my novel blowout means is connected in series with the cooperating contacts of the circuit breaker. This type of circuit connection is utilized in FIGURES 1, 2, 4 and 5 in the following manner: the input terminal is shown as parallel connected terminals 72 and 74, respectively (FIGURE 5). Terminal 72 is connected to plate 46 by means of bolts 76 and 78, while terminal 74, seen in FIGURE 5, is connected to plate 48 by means of bolts 80 and 82. The current path then follows the plates 46 and 48 in a substantially U-shaped path, and the ends of plates 46 and 48 are connected to either side of contact 42. This is best seen in FIGURE 2 where bolt means 86 and 88 extend through and electrically connect plate 46 to stationary contact 42, while a pair of bolt members, of which only bolt member 90 is visible, extend through plate member 48 and stationary contact 42 to form the electrical connection to the stationary contact 42.

The stationary contact 42 is supported from a cradle support 92 which is held in turn by member 93 (FIG- URES l and 5) which is fastened to terminals 72 and 74. Cradle support 92 has protrusions 94 and 96 extending therefrom to receive plate 98 in bolted relationship, plate 98 having the stationary contact 42 rigidly fastened thereto.

Hence, the current path in the structure of FIGURE 1 extends from the terminals 72 and 74, plates 46 and 48 (FIGURE 5), stationary contact 42, movable contact 36, and thence from movable contact 36 to lower terminal 100 which is electrically connected to the movable contact 36. Therefore, it is seen that the structure of FIG- URES 1, 2, 4 and 5 forms an electrical circuit identical to the schematically indicated circuit of FIGURE 6.

In order to prevent accidental electrical contact between the plates 46 and 48 and the movable contact structure, insulating sheets such as sheets 102 and 104 surround the left-hand portion of plate 46, as seen in FIG- URE' 5. In a similar mannenthe plate 48 is adapted with similar insulating sheets 106 and 108.

FIGURE 3 shows the arc chutestructure which is used in conjunction with the mechanism above described for FIGURES 1, 2, 4 and 5. This structure is not shown in the other figures for purposes of clarity. Arc chute means 109 will contain arc plates (not shown) in the well-known manner which arcing plates will extend across the arc chute and have slots extending upwardly and into the arc chute. These arcing plates are not shown in the figure for purposes of clarity, but may be of any desired type, such as those set forth in application Serial No. 557,509 filed January 5, 1956, entitled Ceramic Arcing Plate Assembly, in the name of A. E. Stringfellow, assigned to the assignee of the instant invention, and now abandoned.

In order to guide the travel of the are which is created upon separation of the cooperating contacts, a pair of arc runners 110 and 112 which are associated with the movable contact 36 and stationary contact 4-2, respectively, of FIGURE I extend up the length of the arc chute. The'arc runners will guide the arc in its upwardly extending path when the arc is being stretched because of the magnetic field applied thereto, and the arcing plates containing restricted slotswilloperate to squeeze the arc as it continues upwardly to thus achieve arc extinction because of the squeezing and elongating of the arc.

It will be noted that arc chute means 109 has a slottedear member 114 extending therefrom which cooperates with a relatively stationary pin member 115 which allows thearc chute and blowout structure associated therewith to berotated about pin 115 and with respect to the mov able contact structure to allow ease of maintenance of the circuit breaker.

In operation, I have found that my novel blowout structure as set forth in FIGURES 1 through 5, and as schematically indicated in FIGURE 6, achieves the unexpected result of providing a concentrated magnetic field in the area of a contact during initiation of contact opera tion, and thus initiation of the arc, and further provides a continuously unidirectional field throughout the area of the are chute region where it is necessary to have the unidirectional magnetic field to continue to drive the arc. The magnetic field created by my novel plate is schematically indicated in FIGURE 7 which is a side view of FIGURE 6 with the arrows indicating the direction of the magnetic field.

A further advantage of my novel blowout which is comprised of a substantially fiat plate is that a large surface for heat radiation is achieved. This will allow the current rating of the blowout to be substantially increased over that of a normal winding having the same current density.

The essential distinction of the flat stamped plate form ing the blowout coil in FIGURES l-through 7 from prior stamped. coils of the type shown in the aforementioned US. Patent No. 2,200,070 to Armstrong et al. is-that the area of the window opening is relatively small with respect to the total area of the plate before the window is removed therefrom, In addition to this, the dimension of the plate from the opening and in the direction of motion of the arc is of the same order of magnitude as is the dimension of the opening.

Thus, in-FIGURE l the dimension A of the plate from the window opening and in the direction of motion of the arc is substantially equal to the dimension B.which is the dimension across the window in the direction of motion, of the arc. Note that exact equality of dimensions A and B is not necessary, and there can be some variation. By way of example, dimension A can be larger than dimension B, while, on the other hand, dimension A can be somewhat less than dimension B. Thus, I define the relationship between these two dimensionsbeing of substantially the same order of magnitude. This is to distinguish over the Armstrong type of device 8. which I define as showing a stamped plate in which the relatively small width rim left by the large stamped window is not of the same order of magnitude and dimenother end of plate 46, however, instead of being directly connected to the stationary contact 64 of FIGURE 6, is connected to one end of a second substantially U- shaped plate 116, as indicated by the black dot in FIG- URE 8, while plate 48 is connected to a second U-shaped plate 113 in a similar manner.

In order to prevent short circuiting between plates 46 and H6 and 48 and 118, insulating sheets and 122, respectively, are interposed between the first and second turns, as best seen in FIGURE 9. The other end of plates M6 and 118 are then connected to the stationary contact 64 which cooperates with movable contact66.

Accordingly, a first and second turn are connected in series with the cooperating contacts 64 and '70, this type of structure intensifying the magnetic field during the contact opening interval.

It is to be noted that this structure is achieved in FIG- URES 8 and 9 without the use of jump gaps and that both coils are continuously connected in series. Furthermore, this type of structure continues to yield the unexpected unidirectional magnetic field described in FIG URE 7.

I-have found that the initial magnetic field created at the instant of contact opening can be intensified by providing a relatively high permeability path for the generated magnetic flux. This path can be supplied by means of magnetic inserts 124 and 126 of FIGURES 10- and 11 which show the plates 46 and 48 of FIGURES 6 and 7 as adapted with these inserts. It will be noted that the inserts I24 and 126 are fastened to the conductive material of plates 4-6-and 48, respectively, in any desiredmanner so as to form a unitary structure. Since inserts I24 and 126 are positioned adjacent the contact area, the magnetic field near the contact area at the initiation of contact operation will be subtsantially increased. Clearly, the same type of insert construction could be utilized in conjunction with a plate structure such as that set forth in FIGURES 8 or 9 where two turns are utilized.

Although I have described preferred embodiments of my novel invention, many variations and modifications will'now be obvious to those skilled in the art, and I prefer, therefore, to be limited not by the specific disclosure herein but only by the appended claims.

I claim:

1. In a magnetic blowout structure for a circuit breaker; said circuit breaker including a pair of cooperable contacts movable between an engaged and disengaged position; said cooperable contacts being respectively associated with are runner means for guiding an are drawn by said cooperable contacts into an are extinguishing means; 'a current conducting means for generating a magnetic field to drive said are into said are extinguishing means; said current conducting means being positioned adjacent said cooper-able contacts and being connected, in series therewith; said current conducting means being a substantially flat plate having a central opening therein for conducting current in at least a partially circular path; the area of said opening being relatively small with respect to the surface area of said plate; said plate having a dimension from the said opening in the direction of motion of said arc of the same order of magnitude as the diameter across said opening.

2. In a magnetic blowout structure for a circuit breaker; said circuit breaker including a pair of cooperable contacts movable between an engaged and disengaged position; said cooperable contacts being respectively associated with are runner means for guiding an are drawn by said cooperating contacts into an are extinguishing means; a current conducting means for generating a magnetic field to drive said are into said are extinguishing means; said current conducting means being positioned adjacent said cooperable contacts and being connected in series therewith; said current conducting means comprising a flat plate having an opening therein for defining a substantially circular path; the area of said opening being relatively small with respect to the surface area of said plate; said plate having a dimension from the said opening in the direction of motion of said are of the same order of magnitude as the diameter across said opening.

3. In a magnetic blowout structure for a circuit breaker; said circuit breaker including a pair of cooperable contacts movable between an engaged and disengaged position; said cooperable contacts being respectively associated with arc runner means for guiding an are drawn by said cooperable contacts into an are extinguishing means; a current conducting means for generating a magnetic field to drive said are into said are extinguishing means; said current conducting means being positioned adjacent said cooperable contacts and being connected in series therewith; said current conducting means being a substantially flat plate having a central opening therein for conducting current in at least a partially circular path; said magnetic blowout structure generating a relatively high magnetic field at the area including said cooperating contacts when said cooperating contacts are disengaged; the area of said opening being relatively small with respect to the surface area of said plate; said plate having a dimension from the said opening in the direction of motion of said are of the same order of magnitude as the diameter across said opening.

4. In a magnetic blowout structure for a circuit breaker; said circuit breaker including a pair of cooperable contacts movable between an engaged and disengaged position; said cooperable contacts being respectively associated with arc runner means for guiding an are drawn by said cooperable contacts into an arc extinguishing means; a current conducting means for generating a magnetic field to drive said are into said are extinguishing means; said current conducting means being positioned adjacent said cooperable contacts and being connected in series therewith; said current conductive means being a first and second substantially flat plate positioned on either side of said cooperating contacts and having openings therein for defining substantially circular current paths therethrough; the area of said openings being relatively small with respect to the surface area of their said respective plates; said plates having a dimension from said opening in the direction of motion of said are of the 10 same order of magnitude as the diameter across said opening.

5. In a magnetic blowout structure for a circuit breaker; said circuit breaker including a pair of cooperable contacts movable between an engaged and disengaged position; said cooperable contacts being respectively associated with arc runner means for guiding an arc drawn by said cooperable contacts into an arc extinguishing means; a current conducting means for generating a magnetic field to drive said are into said are extinguishing means; said current conducting means being positioned adjacent said cooperable contacts and being connected in series therewith; said current conductive means being a first and second substantially flat plate positioned on either side of said cooperating contacts and having openings therein for defining substantially circular current paths therethrough; said magnetic blowout structure generating a relatively high magnetic field at the area including said cooperating contacts when said cooperating contacts are disengaged; said magnetic blowout structure generating a unidirectional magnetic field throughout the area in which an are drawn by said cooperating contacts is moved when said cooperating contacts are disengaged; the area of said openings being relatively small with respect to the surface area of their said respective plates; said plates having a dimension from said opening in the direction of motion of said are of the same order of magnitude as the diameter across said opening.

6. In a magnetic blowout structure for a circuit breaker; said circuit breaker including a pair of cooperable contacts movable between an engaged and disengaged position; said cooperable contacts being respectively associated with are runner means for guiding an are drawn by said cooperable contacts into an arc extinguishing means, a current conducting means for generating a magnetic field to drive said arc into said are extinguishing means; said current conducting means being positioned adjacent said cooperable contacts and being connected in series therewith; said current conducting means comprising a fiat plate having an opening therein for defining a substantially circular path; the area of said opening being relatively small with respect to the surface area of said plate; said plate having a dimension from the said opening in the direction of motion of said are of the same order of magnitude as the diameter across said opening; said plate portion adjacent said cooperating contacts being associated with a member of magnetic material.

References Cited in the file of this patent UNITED STATES PATENTS 1,996,112 Jensen et :al. Apr. 2, 1935 2,147,430 Ellis et a1 Feb. 14, 1939 FOREIGN PATENTS 588,261 France Jan. 28, 1925 888,694 France Sept. 13, 1943 

